linux-kernel - Re: [PATCH 1/2] freezer: add unsafe versions of freezable helpers

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Message-ID: <20130504225549.GA24276@amd.pavel.ucw.cz>
Date:	Sun, 5 May 2013 00:55:49 +0200
From:	Pavel Machek <pavel@....cz>
To:	Colin Cross <ccross@...roid.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Len Brown <len.brown@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mandeep Singh Baines <msb@...omium.org>,
	Paul Walmsley <paul@...an.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-nfs@...r.kernel.org,
	Linux PM list <linux-pm@...r.kernel.org>,
	netdev@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Ben Chan <benchan@...omium.org>
Subject: Re: [PATCH 1/2] freezer: add unsafe versions of freezable helpers

Hi!

> >> NFS calls the freezable helpers with locks held, which is unsafe
> >> and caused lockdep warnings when 6aa9707 "lockdep: check that no
> >> locks held at freeze time" was applied (reverted in dbf520a).
> >> Add new *_unsafe versions of the helpers that will not run the
> >> lockdep test when 6aa9707 is reapplied, and call them from NFS.
> >>
> >> Signed-off-by: Colin Cross <ccross@...roid.com>
> >
> > Looks mostly good.
> >
> >> @@ -152,6 +169,14 @@ static inline bool freezer_should_skip(struct task_struct *p)
> >>       freezer_count();                                                \
> >>  })
> >>
> >> +/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
> >> +#define freezable_schedule_unsafe()                                  \
> >> +({                                                                   \
> >> +     freezer_do_not_count();                                         \
> >> +     schedule();                                                     \
> >> +     freezer_count_unsafe();                                         \
> >> +})
> >> +
> >
> > Make it inline function? :-). Add short explanation why it is good
> > idea?
> 
> These are exact copies of the existing non-unsafe versions, except
> they call freezer_count_unsafe() instead of freezer_count().  The next
> version of my other patch stack that goes on top of this has a patch
> to convert the macros in this file to static inline functions (at
> least the ones that can be).  I'd rather not mix it in with this patch
> for ease of comparison with the existing calls.

Ok.

Acked-by: Pavel Machek <pavel@....cz>

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